nope not much use after around 3 months as they start to make new noises as it all changes, i found that MJ made very similar noises for tired, hungry and upper wind pain....
around 3 months babies start to experiment wth sounds and so the basic ones are not made as much....

the thing is that after 3 months you know the other signs or cues that your baby gives for certian things, and obviously your ay does just wake up one morning and not make the sounds, its a gradual thing and you learn as you are going iykwim

Amberj, its hard isnt it, just when you think that you have something figured t all changes again